Adjustable staircase



Oct. 7, 1969 J. WHITEHEAD ADJUSTABLE STAIRCASE 2 Sheets-Sheet 1 Filed May 23 1968 Oct. 7, 1969 J. WHITEHEAD ADJUSTABLE STAIRCASE 2 Sheets-Sheet 2 Filed May 23 1968 Aqents United States Patent 3,470,664 ADJUSTABLE STAIRCASE John I. Whitehead, R.R. 4, Brantford, Ontario, Canada Filed May 23, 1968, Ser. No. 731,422 Int. Cl. E041? 11/04 US. Cl. 52--183 11 Claims ABSTRACT OF THE DISCLOSURE An adjustable staircase comprises a plurality of stairs each comprising an integral sheet metal unit providing a tread, a riser upstanding from the rear edge of the tread, a rounded toe at the front edge of the tread, and an inwardly inclined apron depending from the lower edge of the toe; these stairs are supported between two parallel stringer structures, each of which structures comprises parallel-connected upper and lower stringers; a pivotal connection is provided between the front end of each stair and said upper stringer, and another pivotal connection is provided between the rear end of each stair and said lower stringer; there are also provided means for connecting the upper end of said upper stringers to an upper floor with an adjustable connection; and means for adjustably securing the lower ends of said lower stringers to a lower floor; the length of the stringer structures can be accommodated to different spacings between the floors and the stairs will automatically remain level.

Field of the invention The present invention relates to adjustable staircases and especially to a metallic staircase comprising elements that can be prefabricated oif the job site and assembled on the job with the assurance that the distance between the two connected floor levels is accurately bridged, each stair has substantially the same rise as every other stair, and each stair tread is level.

Description of the prior art It is a recognized requirement in the building trade that the rise for each stair of a staircase should be constant and uniform, as compared to the rise of the other stairs, a discrepancy of as little as one-half inch creating an unsatisfactory condition. Moreover, the tread of each stair should be level in all directions. For these reasons, and also because the structural conditions vary with each job, it has usually been necessary for each staircase to be a custom-built structure, and it has been considered impractical, if not impossible, for example, to prefabricate the staircases for a large number of houses in a building development. The same negative view has been taken of making the staircases of sheet metal such as steel, because of the necessity of fitting each staircase to the particular building in which it is installed.

Summary of the invention It is an object of the present invention to provide an adjustable staircase comprising elements that may be prefabricated and assembled on the job site with the assembled staircase being susceptible of adjustment to accommodate the structural conditions of the particular building in which it is installed.

In accordance with the present invention there is provided an adjustable staircase; a plurality of stairs each comprising an integral sheet metal unit providing a tread, a riser upstanding from the rear edge of the tread, a toe at the front edge of the tread, and an inwardly inclined apron depending from the lower edge of the toe; a pair of parallel transversely-spaced upper stringers disposed at respective ends of the said stairs, a pair of parallel transversely-spaced lower stringers disposed at respective ends of the said stairs, each lower stringer being parallel to and operatively associated with a respective upper stringer; a pivotal connection between the front end of each stair and said upper stringer; a pivotal connection between the rear end of each stair and sail lower stringer; means for connecting the upper ends of said upper stringers to a floor beam with an adjustable connection; and means for adjustably securing the lower ends of said lower stringers to a lower floor.

Every staircase includes a stair-supporting parallelogram structure at each side, which, for the purposes of this specification is identified as parallel upper and lower stringers. The stairs are mounted between these stringers and each stair comprises a tread and a riser. The tread of the lowermost stair must be accurately positioned relative to the floor surface from which the staircase rises and the tread of the top stair must be similarly positioned relative to the upper floor surface. Moreover, each stair must have the same rise as all the other stairs.

Preferably, each sheet metal stair comprises a tread with a rounded toe at its forward or exposed edge.

As both the tread and rise of a stair are of sheet metal it becomes necessary to reinforce them to add rigidity to the structure. Preferably there is provided in a staircase of the kind described, a reinforcing member at each side edge of each riser. These reinforcing members preferably take the form of angle members. A central bracing member for each tread may be provided in the form of a sheet metal channel member that extends transversely under each tread.

An adjustable connection may be provided between the member reinforcing the risers and the upper stringer, such a connection taking the form of slightly arcuate slots in the angle members which receive bolts on the risers.

The apron which depends from the rounded toe overlies the upper edge of the riser of the stair next below to accommodate adjustment of the riser while still affording a finished appearance.

It is essential that an installed staircase otter a finished appearance at the top with the floor edge having the same structural characteristics as the toes of the stairs. Thus the connecting means for the: upper end of the staircase may comprise an upper toe piece together with brackets on which it is mounted and which brackets also provide anchorage for the upper ends of the stringers.

In installing the adjustable staircase of this invention the structure at the top is first secured. This means that the effective length of the stringer structure must then be adjusted to bring the tread of the lowermost stair to the proper height above the floor, when it can be fixed in this position. With this factor in mind, an adjustable staircase in accordance with this invention comprises a base plate, the lower edge of which engages the floor, there being a base plate at each side, a. bracket at each side secured at its upper edge to the angle members of the lowermost tread and connected to the base plate by adjustable connections, and a base plate actuator at each side which is pivotally mounted on the bracket at the respective side by a fixed pivot and connected at the bottom to the base plate and lower stringer by adjustable connections.

Various other more detailed objects and advantages of the invention, such as arise in connection with carrying out the above ideas in a practical embodiment, will in part become apparent, and in part be hereinafter stated, as the description of the invention proceeds.

Description of the drawings A particular preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIGURE 1 is a perspective view from above and to one side of a complete adjustable staircase, parts thereof being shown broken away and in exploded relation as necessary for clarity of illustration,

FIGURE 2 is another perspective view looking up from below with the staircase shown as cut down the centre and with parts broken away,

FIGURE 3 is a side elevation of a staircase adjusted to fit between two relatively close floor levels, and

FIGURE 4 is a view similar to FIGURE 3 showing the same staircase fitted between two more widely spaced floor levels.

Description of the preferred embodiment Referring now to the drawings, wherein like reference characters denote corresponding parts, a beam supporting an upper floor 11 is shown in FIGURES l, 3 and 4, while the corresponding lower floor is indicated by reference 12.

A pair of transversely-spaced upper stringers 13 of sheet metal (such as steel), each having a top out-turned flange 14, are of suflicient length to bridge the space between adjacent floor levels, each stringer being disposed on a respective side of the stair. A side piece 9 is pivotally connected to the lower end of each upper stringer 13, the pivot being indicated by reference 8 in FIGURE 1, while the upper end of each stringer is anchored to the beam 10 by a bracket 15. This bracket is formed with a flange 16 having holes (FIGURE 2), through which pass fastening screws 18 embedded in the wood of the beams, and is also formed with an arcuate slot 19 through which passes a bolt 20 carried by the upper stringer 13. This bolt and slot connection permits pivotal adjustment of the upper stringer relative to the beam 10, and after a desired adjustment is achieved a nut (not illustrated) is applied to the bolt and tightened to secure the connection.

The staircase also comprises a pair of parallel, transversely-spaced lower stringers 21, respectively of angular cross section and having a vertical flange 22, each lower stringer being disposed parallel to and operatively associated with a respective upper stringer 13, and each carrying a bolt 23 at its lower end.

An individual stair is identified by the reference character S, and a plurality of similar stairs are mounted between the pairs of parallel stringers 13 and 21. Each stair S comprises a tread 24 of sheet steel, a riser 25 integral with the tread 24 and integrally joined thereto at its rear edge, a rounded toe portion 26 integrally connected to the front edge of the tread 24, and an inwardly inclined apron 27 integrally joined to the toe portion 26. The shape of the apron 27 is made such that it will always be held by its own resilience in close engagement with the upper end of the riser of the next lowest step and effectively completes and closes the riser.

A brace 29 in the form of a sheet steel channel bar extends transversely across each tread 24 on the underside thereof, the brace having side flanges 30 which are welded to the tread to secure the connection. An edge reinforcement is provided at each side of the tread 24 in the form of an angle bar 31, the top flange of which is welded to the underside of the tread. A bolt 32 pivotally connects the front end of each angle bar 31 to the respective top stringer 13, while a bolt 33 pivotally connects the rear end of each angle bar 31 to the associated lower stringer.

The riser 25 is reinforced at each side by an angle plate 34 having a flange welded to the rear face of the riser, each plate 34 being formed with an arcuate slot 35 which receives a bolt 36 carried by the upper stringer 13. As in the case of the bolts 32 and 33 the bolts 36 are provided with nuts which are loosened to permit adjustment and tightened to secure an adjustment.

A bracket plate 37 is anchored to the inner face of each angle bar 31 of the lowermost stair S, this anchorage being achieved in any preferred way, as by welding. The brackets plate 37 carries two bolts 38 and 39, by which the plate 37 is connected to base plate 40 having a bottom flange 41 (FIGURE 2) that rests on the floor 12. The base plate 40 has two arcuate slots 42 and 43 which receive the bolts 38 and 39, while the flange 41 is formed with openings 7 which accommodate screws (not illustrated) to anchor the base plates to the floor 12 after final adjustment of the stringers. The base plate 40 is also provided with another slot 44.

A base plate actuator 45 is pivotally mounted on the bolt 23 with the latter constituting a fixed pivot, the actuator being of generally triangular shape with the pivot at 23 at the lower corner thereof. A forward upper corner of the actuator 45 is formed with a slot 46 which receives the pin 47 on the upper stringer 13, while the remaining rearward upper corner of the actuator 45 is formed with a slot 54, through which passes a bolt 62 passing through the said slot 44 in the base plate 40.

A bottom-stair closing piece 48 extends up from the floor 12 to the apron 27 of the lowermost stair 5, while a top finishing piece 49, comparable to the toe and apron of a tread, extends from the upper floor 11, the piece 49 including a flat portion that is flush with the floor 11 and a flange 50 that depends therefrom and abuts the edge of the flooring 11.

Each base plate 40 is cut away at its forward upper corner to leave a front edge that is shorter than the height of the remainder of the base plate (as shown in FIGURES 2, 3 and 4), and a flange 51 (FIGURE 2) formed with openings is integrally joined to this short front edge. Fastening elements such as bolts 53 pass through the openings in the flange 51 and corresponding holes in the face plate 48 to mount the latter across the base plates at the bottom of the staircase.

Each bracket 15 is formed at its upper edge, closely adjacent to the flange 16, with an integral tab 55 that extends inwardly therefrom parallel to the stairs, these tabs 55 performing a supporting function now to be described. An upper stringer support is referred to in its entirety by the reference character V, and one of these supports V is provided at each side of the stair. Each support V comprises a main body portion 56 which is vertical when installed and is formed with an aperture receiving a pivot bolt 58 passing through the upper stringer 13.

A flange 59 is integral with the upper edge of the main body 56 of each support V and supportingly engages the underface of the toe piece 49 (FIGURE 2), while a flange 60 extends outwardly from the lower edge of the main body 56 and rests on the tabs 55, to which they are secured, as by bolting. Each flange 60 is continued out beyond the main body 56 and is formed with a skirt 61 which overlies the end of the adjacent tab 55.

It will be seen that the supports V provide the main pivotal supports for the upper ends of the upper stringers 13 via the pivot bolts 58. The connection constituted by bolt 18, slot 19 and nut 20 merely permits adjustment of the upper stringers about the pivot 58, and after each adjustment the bolts 20 are tightened to secure the connection.

As explained above, the upper stringers are effectively pivoted at their upper ends to the upper floor 11 via the bolts 58, while they are pivoted at their lower ends to the lower floor 12 via the lowermost pivot bolts 32, these lowermost bolts being carried by the reinforcements 31 that are secured to the base plates 40. Each parallel lower stringer is pivoted at its upper end by the uppermost bolt 33 effectively to the upper floor level at a location almost vertically below the pivot 58, and is pivoted effectively to the lower floor level via the bolt 23. The special connection of the bolt 23 to the piece 45, and the adjustable cam slot connection of the piece 45 to the base plate 40, is required because of the difliculty in practice of locating the bolt 23 in a position relative to the pivot 32 corresponding to the relative position of the pivots 58 and 33, so as to obtain a true parallelogram linkage. The spacing of immediately adjacent pairs of bolts 32 or 33 are made the same, while the distance between each two associated bolts 32 and 33 on the same reinforcement 31 are the same, so that the treads 24 carried by the reinforcements must remain parallel to one another as the stringers are adjusted in parallelogram linkage manner, as illustrated by FIGURES 3 and 4.

In the practical application of the invention, a staircase will be selected that has the number of stairs required to accommodate the height between the floors to be bridged. For a specific example, a five stair staircase that has actually been constructed can be fitted between levels spaced from 32.46 to 39.37 inches, while a six stair embodiment will fit from 38.95 to 47.25 inches. The following procedure for installation is recommended:

(1) All of the bolts 20, 23, 32, 33 and 36 on the stringers are loosened to the extent of about one revolution.

(2) The beam is now checked to ensure that it is level and in correct vertical alignment. Should any discrepancies develop they can be corrected by using wedges or by trimming certain parts.

(3) The fasteners V and the brackets are fixed in position and the assembled staircase is now fixed into position so that the upper surface of the piece 49 is flush with the flooring -11 and is level.

(4) If the staircase interferes with a sidewall of the staircase well that is not square with the beam 10, either one or both of the brackets 15 may be adjusted by inserting shims beneath the respective flange 16.

(5) The base plates 40 are now lowered until the flanges 41 rest on the floor. The tread 24 of the lowermost stair S is now leveled transversely, if necessary either or both of the base plates being adjusted by inserting shims beneath the respective flange 41.

(6) The level of the tread 24 of an intermediate stair S is now checked in the direction between the toe 26 and its riser 25, any necessary adjustment being made for example by lightly tapping the tread to move it upwardly or downwardly, this movement being accommodated by the bolts 36 moving in slots 35. This should achieve accurate leveling of the treads in both directions.

(7) All bolts are now securely tightened.

(8) The flanges 41 of the base plates 40 are screwed to the floor.

It is evident that because of the above-described parallelogram construction the rise for all the stairs is the same and the treads of all the stairs are level, while the upper edge of the riser for the top stair is finished and flush with the upper floor surface.

While a preferred specific embodiment of the invention is hereinbefore set forth, it is to be clearly understood that the invention is not to be limited to the exact constructions, mechanisms, and devices illustrated and described because various modifications of these details may be provided in putting the invention into practice within the scope of the appended claims.

What I claim is:

1. In an adjustable staircase; a plurality of stairs each comprising an integral sheet metal unit providing a tread, a riser upstanding from the rear edge of the tread, a toe at the front edge of the tread, and an inwardly inclined apron depending from the lower edge of the toe; a pair of parallel transversely-spaced upper stringers disposed at respective ends of the said stairs, a pair of parallel transversely-spaced lower stringers disposed at respective ends of the said stairs, each lower stringer being parallel to and operatively associated with a respective upper stringer; a pivotal connection between the front end of each stair and said upper stringer; a pivotal connection between the rear end of each stair and said lower stringer; means for connecting the upper ends of said upper stringers to a fioor beam with an adjustable connection; and means for adjustably securing the lower ends of said lower stringers to a lower floor.

2. The adjustable staircase of claim 1, in which each tread is braced by a transverse channel. member on the underside thereof.

3. The adjustable staircase of claim 1, in which each stair tread comprises a reinforcing member at each end on the underside thereof, and the said pivotal connections of the stringers to the stairs are to the front and rear portions respectively of the reinforcing members.

4. The adjustable staircase of claim 1, in which each said stair sheet metal unit is provided at the rear face of each edge of the riser with a reinforcing plate formed with an arcuate slot, and an adjustable connection between each upper stringer and the adjacent reinforcing plate.

5. The adjustable staircase of claim 1, in which the pivotal connections are provided by bolts and nuts.

6. The adjustable staircase of claim 1, in which the means for adjustably securing the lower end of each lower stringer to a floor comprises a bracket plate at each side of the tread of the lowermost stair and anchored thereto; a base plate adjustably mounted on each bracket plate; and a base plate actuator pivotally mounted on said lower stringer and connected to said base plate and upper stringer by adjustable connections.

7. The adjustable staircase of claim 6, in which each base plate is adjustably mounted on its respective bracket plate by means comprising a pair of bolts and a pair of corresponding parallel arcuate slots in the base plate receiving the bolts.

8. The adjustable staircase of claim 6, in which the lower end of the lower stringer carries a bolt that is received in a hole in the actuator and the actuator carries a bolt that is received in a hole in the base plate and a bolt that is received in a hole in the upper stringer.

9. The adjustable staircase of claim 1, in which the means for adjustably connecting the upper ends of the upper strings to a floor beam comprises a pair of brackets, each of which is adapted to be anchored to the beam and each of which has a slot receiving a bolt carried by each of the upper stringers.

10. The adjustable staircase of claim 1, together with a finishing toe piece adapted to be secured to the upper floor with a fiat portion flush with the floor surface and to which is integrally joined a rounded toe from which depends an apron passing over the upper edge of the adjacent riser.

11. In an adjustable staircase; a plurality of stairs each comprising a unit providing a tread, a riser upstanding from the rear edge of the tread, a rounded toe at the front edge of the tread, and an inwardly inclined apron depending from the lower edge of the toe; a reinforcing bar on the underside of the tread at each side thereof; a reinforcing plate on the rear face of the riser at each edge thereof and formed with a slot; a pair of parallel transversely-spaced upper stringers disposed at respective ends of the said stairs, a pair of parallel transversely-spaced lower stringers disposed at respective ends of the said stairs, each lower stringer being parallel to and operatively 7 8 associated with a respective upper stringer; bolts on said References Cited upper stringer received in said slot in the reinforcing UNITED STATES PATENTS plates; a pivotal connection between the front end of a h reinforcing bar and said upper stringer; a pivotal 538145 4/1895 Allen 52182 connection between the rear end of each reinforcing bar 5 624782 5/1899 Fuchs 52.483 and said lower stringer, whereby the said upper and 2245825 6/1941 Ross 52*183 lower stringers and the stairs constitute an effective paral- FOREIGN PATENTS lelogram llnkage, means for connecting the upper end of 94,624 1959 Norway said upper stringer to an upper floor with an adjustable connection; and means for adjustably securing the lower 10 JOHN E MURTAGH Primary Examiner end of said lower stringer to a lower floor. 

